Here we will discuss and show you how to figure out which number is a factor of 21, but not a multiple of 78.
The most common way to determine which number is a factor of 21, but not a multiple of 78, is to simply list the factors of 21 and the multiples of 78 so you can compare the two lists.
The answer to "Which number is a factor of 21, but not a multiple of 78?" would be all the numbers that are on the Factors of 21 list, but not on the Multiples of 78 list.
Factors of 21: 1, 3, 7, 21
Multiples of 78: 78, 156, 234, 312, 390...
Answer: 1, 3, 7, 21
Alternatively, you can figure out which number is a factor of 21, but not a multiple of 78, by dividing every factor of 21 by 78. The answer would be all the quotients that are not integers.
Factor, but not a Multiple
You can submit another "Which number is a factor, but not a multiple?" problem below.
Which number is a factor of 22, but not a multiple of 78?
Here is a similar problem in our Multiples database that we have solved for you.